Organic electroluminescent device and method of manufacturing the same

ABSTRACT

An organic electroluminescent device and its method of manufacturing are provided. The organic electroluminescent device may include a rear substrate, an organic electroluminescent unit including a first electrode, an organic film, and a second electrode stacked on a surface of the rear substrate. It may also include a front substrate joined to the rear substrate to seal an internal space in which the organic electroluminescent unit is disposed. It may also include a porous oxide layer composed of a porous silica and a metal compound on a lower surface thereof. A device constructed according to the present invention may have excellent adsorption of moisture and oxygen, thereby increasing the life span of the device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 10/932,111, filed on Sep. 2, 2004, and claims priority toKorean Patent Application No. 2003-61368, filed on Sep. 3, 2003, in theKorean Intellectual Property Office, which are all incorporated hereinby reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic electroluminescent deviceand a method of manufacturing the same. More particularly, the presentinvention relates to an organic electroluminescent device including aporous oxide layer, with an extended life span due to an improvement inmoisture and oxygen adsorption, and to a method of manufacturing thesame.

2. Description of the Invention

Organic electroluminescent (EL) devices are self emission displays thatemit light by recombination of electrons and holes in a thin layer madeof a fluorescent or phosphorescent organic compound when current isapplied to the thin layer. Organic EL devices have advantages such aslightweight, simple constitutional elements, ease of fabrication,superior image quality, and wide viewing angle. In addition, organic ELdevices have electrical properties suitable for portable electronicequipment such as high quality dynamic images, high color purity, lowpower consumption, and low driving voltage.

However, organic EL devices are easily deteriorated by the entry ofmoisture. Therefore an encapsulation structure for preventing the entryof moisture is required.

Conventionally, a metal can or a glass substrate etched in the form of acap with a groove is used for encapsulation. In such a case, formoisture adsorption, a desiccant of a powder type is mounted in thegroove or a desiccant of a film type is adhered in the groove by meansof a double-sided tape. However, the process of manufacturing with apowder-type desiccant is complicated, and material and process costs arehigh. In addition, the thickness of the substrate increases andsubstrates intended for encapsulation are not transparent, which rendersfront emission difficult. On the other hand, the film-type desiccantinsufficiently prevents the entry of moisture and the desiccant may beeasily broken during fabrication or use, thereby lowering durability andreliability, and rendering mass production difficult. In addition to theabove problems, even though use of a metal can may ensure structuralfirmness, the etched glass is structural weak and may be easily damagedby external impact.

Japanese Patent Laid-Open Publication No. Hei. 9-148066 discusses anorganic EL device including a laminate having a pair of electrodesopposite to each other and an organic light-emitting material layer madeof an organic compound interposed between the electrodes, an airtightcontainer for preventing exposure of the laminate to the air, and dryingmeans made of, for example, alkaline metal oxide, disposed in theairtight container. However, the bulky shape of the airtight containerincreases the total thickness of the organic EL device. Also, opaquenessof the drying means renders the fabrication of a front emission typeorganic EL device difficult, even though the drying means is maintainedin a solid state after adsorbing moisture. In addition, the fabricationprocess is complicated, increasing material and process costs.

SUMMARY OF THE INVENTION

The present invention provides an organic EL device with an improvementin the adsorption of moisture and oxygen, which can be used for frontemission.

The present invention also provides a method of manufacturing theorganic EL device.

According to an aspect of the present invention, there is provided anorganic EL device comprising: a rear substrate; an organic EL unitcomprising a first electrode, an organic film, and a second electrodestacked on a surface of the rear substrate; and a front substrate joinedto the rear substrate to seal an internal space in which the organic ELunit is disposed and having a porous oxide layer composed of a poroussilica and a metal compound on a lower surface thereof.

According to an aspect of the present invention, there is provided anorganic electroluminescent device comprising: a rear substrate; anorganic electroluminescent unit comprising a first electrode, an organicfilm, and a second electrode stacked on a surface of the rear substrate;and a front substrate joined to the rear substrate to seal an internalspace in which the organic electroluminescent unit is disposed, using ansealant; a porous oxide layer composed of a porous oxide layer composedof a porous silica and a metal compound disposed in the internal spaceformed by the rear substrate and the front substrate.

The porous oxide layer is formed on an internal space of the rearsubstrate, lateral surfaces of the sealant, or at least one of the rearsubstrate or the front substrate.

According to another aspect of the present invention, there is provideda method of manufacturing an organic EL device, comprising: preparing arear substrate having, on a surface thereof, an organic EL unitcomprising a first electrode, an organic film, and a second electrodestacked; coating a composition for porous silica formation comprising asilicon alkoxide and a polar solvent on a lower surface of a frontsubstrate followed by thermal treatment to form a porous silica layer;coating a sealant on at least a side of each of the rear substrate andthe front substrate corresponding to outside the organic EL unit; andjoining the rear substrate and the front substrate.

The composition for porous silica formation may further comprisealkaline metal salt, alkaline earth metal salt, metal halide, metalsulfate, and/or metal perchlorate.

The composition for porous silica formation may further comprise anacrylic resin as a stabilizer.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent in the following detailed description withreference to the attached drawings.

FIGS. 1A, 1B, and 1C are a schematic sectional view that illustrates anexample of an organic EL device according to the present invention.

FIG. 2 is a perspective view of a porous silica layer used in an organicEL device according to the present invention.

FIG. 3 is a microphotograph showing luminance reduction and dark spot orpixel shrinkage with time in an organic EL device according to Example 1of the present invention.

FIG. 4 is a transmission electron microphotograph (TEM) of themicrostructure of a porous silica layer in the organic EL deviceaccording to Example 1 of the present invention.

FIG. 5 is a microphotograph showing luminance reduction and dark spot orpixel shrinkage with time in an organic EL device according toComparative Example 1.

DETAILED DESCRIPTION OF THE INVENTION

The method of the present invention may include coating an upper surfaceof the porous silica layer with a composition including one or moreselected from the group consisting of alkaline metal salt, alkalineearth metal salt, metal halide, metal sulfate, and metal perchlorate,and a solvent. Thus a layer made of, for example, alkaline metal oxideand/or oxide thereof, alkaline earth metal oxide and/or oxide thereof,metal halide and/or oxide thereof, metal sulfate and/or oxide thereof,and metal perchlorate and/or oxide thereof may be further formed on theporous silica layer. Alternatively, alkaline metal oxide, alkaline earthmetal oxide, metal halide, metal sulfate, or metal perchlorate may beconfined in a porous silica network.

The composition for silica formation may further include 0.1 to 0.9moles of a catalyst for facilitating a hydrolysis reaction, for eachmole of the silicon alkoxide. Moreover, the thermal treatment may beperformed at a temperature of 100 to 550° C. Additionally, the siliconalkoxide may be tetramethylorthosilicate (TMOS) ortetraethylorthosilicate (TEOS).

The organic EL device of the present invention may include a porousoxide layer with excellent adsorption of moisture and oxygen. The porousoxide layer may be made of a porous silica layer and a metal compoundlayer with adsorption, or a porous silica network and a metal compoundconfined in the porous silica network. Thus the porous oxide layer canpromote both physisorption and chemisorption, thereby increasing theadsorption of moisture and oxygen. In particular, in the case of theporous oxide layer composed of porous silica, silanol groups distributedin pore walls of the porous oxide layer play a role in the adsorption ofmoisture and oxygen. The present invention provides a method ofmanufacturing an organic EL device that includes a porous oxide layercomposed of porous silica alone and having a thick thickness of 0.1 to12 μm. According to this method, a thick film can be obtained withoutperforming multi-coating, thereby ensuring a porous oxide layeruniformly coated on a wide area.

As shown in FIG. 1, an organic EL device may include a rear substrate 10made of a glass or a transparent insulating material, an organic EL unit12 including a first electrode, an organic film, and a second electrodestacked on a surface of the rear substrate 10, and a front substrate 11joined to the rear substrate 10 to seal a space in which the organic ELunit 12 is disposed and having a porous oxide layer 13 on a lowersurface thereof. The front substrate 11 and the rear substrate 10 arejoined by a sealant 14 coated outside the organic EL unit 12.

The front substrate 11 may also be called an encapsulating substrate,and may have a sealing capability in conjunction with the rear substrate10 for the organic EL unit 12 disposed therebetween. The front substrate11 may take form of an encapsulating substrate, as shown in FIG. 1B.Front substrates 21 and 31 shown in FIGS. 1B and 1C may also act asencapsulating substrates like front substrate 11 shown in FIG. 1A.

As shown in FIG. 1B, the organic EL device according to the presentinvention includes a rear substrate 20, the front substrate 21, anorganic EL unit 22, and a porous oxide layer 23 formed on the lateralsurface of the sealant 24.

As shown in FIG. 1C, the organic EL device according to the presentinvention has a plurality of recesses 35 formed on one surface of therear surface 31, that is, an encapsulating substrate, sealed with thefront substrate 30 to form an internal space, and a porous oxide layer33 is formed in the plurality of recesses 35. The device also includesan organic EL unit 32 and a sealant 34.

The organic EL unit 12 may be formed by deposition and has a stackedstructure of a first electrode, an organic film, and a second electrode.The first electrode may be a cathode and the second electrode may be ananode. The organic film may include a hole injection layer, a holetransport layer, a light-emitting layer, an electron injection layer,and/or an electron transport layer.

The front substrate 11 may be made of an insulating material, forexample, a glass or a transparent plastic material. The front substrate11 (in this case made of a transparent plastic material) may be formedwith a protective film on a lower surface thereof to prevent the entryof moisture. The protective film may be resistant to heat, chemicals,and humidity. The front substrate made of a transparent material can beused for front emission.

For rear emission, the organic EL unit 12 may have the first electrodemade of a transparent material and the second electrode made of areflective material. On the other hand, for front emission, the organicEL unit 12 may have the first electrode made of a reflective materialand the second electrode made of a transparent material. The firstelectrode may be disposed near the rear substrate 10 and the secondelectrode may be disposed near the front substrate 11.

On an upper surface, the second electrode may have a protective film forplanarization of organic EL unit 12 to provide resistance to heat,chemicals, and humidity. The protective film may be made of an inorganicmaterial such as metal oxide or metal nitride.

The space defined by the front substrate 11 and the rear substrate 10may be in a vacuum state or filled with an inert gas.

Preferably, the porous oxide layer 13 has a thickness of approximately0.1 to about 12 μm. If the thickness of the porous oxide layer 13 isless than 0.1 μm, adsorption may be insufficient. On the other hand, ifit exceeds 12 μm, the porous oxide layer may contact the cathode, andthe area for moisture permeation may be increased.

The porous oxide layer may be composed of a porous silica and a metalcompound. The metal compound may be one or more of the following:alkaline metal oxide, alkaline earth metal oxide, metal halide, metalsulfate, or metal perchlorate.

The porous oxide layer may have a two-layer structure including a poroussilica layer and a metal compound layer, for example, a porous silicalayer and a calcium oxide layer. The porous oxide layer may also beformed so that the metal compound is confined in a network of the poroussilica.

In the porous oxide layer composed of the porous silica and the metalcompound, the weight ratio of porous silica to metal compound maypreferably be in a range of approximately 0.1:1 to about 1:1, but is notlimited thereto.

The alkaline metal oxide may, for example, be lithium oxide (Li₂O),sodium oxide (Na₂O), or potassium oxide (K₂O), and the alkaline earthmetal oxide may be barium oxide (BaO), calcium oxide (CaO), or magnesiumoxide (MgO). The metal sulfate may, for example, be lithium sulfate(Li₂SO₄), sodium sulfate (Na₂SO₄), calcium sulfate (CaSO₄), magnesiumsulfate (MgSO₄), cobalt sulfate (CoSO₄), gallium sulfate (Ga₂(SO₄)₃),titanium sulfate (Ti(SO₄)₂), or nickel sulfate (NiSO₄). The metal halidemay, for example, be calcium chloride (CaCl₂), magnesium chloride(MgCl₂), strontium chloride (SrCl₂), yttrium chloride (YCl₂), copperchloride (CuCl₂), cesium fluoride (CsF), tantalum fluoride (TaF₅),niobium fluoride (NbF₅), lithium bromide (LiBr), calcium bromide(CaBr₃), cerium bromide (CeBr₄), selenium bromide (SeBr₂), vanadiumbromide (VBr₂), magnesium bromide (MgBr₂), barium iodide (BaI₂), ormagnesium iodide (MgI₂). The metal perchlorate may, for example, bebarium perchlorate (Ba(ClO₄)₂) or magnesium perchlorate (Mg(ClO₄)₂).

A method of manufacturing an organic EL device including theabove-described porous oxide layer will now be described in detail.First, a first electrode, an organic film, and a second electrode may bestacked on a rear substrate to form an organic EL unit on the rearsubstrate. Then a composition including a silicon alkoxide and a polarsolvent may be coated on a lower surface of a front substrate. This maybe followed by thermal treatment to form a porous silica layer. Theporous silica layer may be formed by hydrolysis of the silicon alkoxide,and dehydration and polycondensation of the hydrolyzed product.

During the thermal treatment, a polymer or an organic material may beremoved and dehydration and polycondensation may occur. Preferably, thethermal treatment may be performed at a temperature of about 100 toapproximately 550° C. If the temperature for the thermal treatment isless than 100° C., an organic material such as the solvent may remain inthe porous silica layer. On the other hand, if it exceeds 550° C., aglass for a substrate may be deformed.

The composition for silica formation may be coated using a spin coatingor screen printing process, but is not limited thereto.

The silicon alkoxide may be represented by Formula 1 below and may beTEOS, TMOS, or a mixture thereof:

Wherein R₁, R₂, R₃, and R₄ are independently an alkyl group of C₁-C₂₀ oran aryl group of C₆-C₂₀.

The polar solvent for silica formation may be one or more selected fromthe group consisting of ethanol, methanol, butanol, isopropanol,methylethylketone, and pure water and may be used in an amount of 100 to1,000 parts by weight, for each 100 parts by weight of the siliconalkoxide.

The composition for silica formation may further include a catalyst forfacilitating a hydrolysis reaction, for example, nitric acid,hydrochloric acid, phosphoric acid, or sulfuric acid. The catalyst maybe used in an amount of approximately 0.1 to about 0.9 moles, for eachmole of the silicon alkoxide. If the content of the catalyst forfacilitating a hydrolysis reaction is less than 0.1 moles, the processduration may increase. On the other hand, if it exceeds 0.9 moles,process control may be difficult.

The composition for silica formation may further include a metalcompound, e.g., one or more of the following: alkaline metal salt,alkaline earth metal salt, metal halide, metal sulfate, or metalperchlorate. Here, the metal compound may be used in an amount ofapproximately 0.1 to about 0.5 moles, for each mole of silicon alkoxide.

Due to the addition of the metal compound such as alkaline metal saltand alkaline earth metal salt to the composition for silica formation,an obtained porous oxide layer may be formed such that the metalcompound with adsorption may be confined in a porous silica network, ormay have a multi-layer structure including a porous silica layer and ametal compound layer. Thus excellent adsorption of moisture and oxygencan be ensured.

The alkaline metal salt may be a precursor of alkaline metal oxide, andmay be potassium acetate, potassium nitrate, sodium acetate, or sodiumnitrate. The alkaline earth metal salt may be calcium acetate, calciumnitrate, barium acetate, or barium nitrate. Examples of the metalhalide, the metal sulfate, and the metal perchlorate are as describedabove.

The composition for silica formation may further include a stabilizersuch as a water-soluble acrylic resin. The stabilizer may be used in anamount of approximately 0.001 to about 50 parts by weight, for each 100parts by weight of the silicon alkoxide.

After forming the porous silica layer, a composition including a metalcompound and a solvent may be coated on the porous silica layer and thenthermally treated. Here, the metal compound may be one or more of thefollowing: alkaline metal salt, alkaline earth metal salt, metal halide,metal sulfate, or metal perchlorate. A metal halide such as CaCl₂ withvery excellent adsorption may be used herein.

After the thermal treatment, a two-layer structure including a poroussilica layer and a metal compound layer may be obtained, or asingle-layer structure in which the metal compound is confined in anetwork of the porous silica layer may be obtained.

The solvent may be water, methoxyethanol, methanol, ethanol, or butanoland may be used in an amount of approximately 100 to about 1,000 partsby weight, for each 100 parts by weight of the metal compound. Thethermal treatment may be performed at a temperature of approximately 100to about 550° C.

The porous oxide layer thus formed may be a thick film with a thicknessof approximately 0.1 to about 12 μm, and may be capable of sufficientadsorption of moisture and oxygen, thereby providing an excellentsealing property for an organic EL device.

After preparing the front substrate with the porous oxide layer asdescribed above, a sealant may be coated on (or otherwise applied to) atleast a side of each of the front substrate and the rear substratecorresponding to outside the organic EL unit, using a screen printer ora dispenser. Then the rear substrate and the front substrate may bejoined to complete an organic EL device of the present invention.

An inner space of the organic EL device thus manufactured may be in avacuum state or filled with an inert gas. Also, after the joining, thesealant may be cured by UV light, visible light, or heat (or any othersuitable means).

The porous silica layer formed as described above is shown in FIG. 2.

As shown in FIG. 2, a porous silica layer 43 may include a silica frame43 a and a plurality of adsorption holes 43 b. The silica frame 43 a mayserve to maintain the structure of the porous silica layer 43.Similarly, the adsorption holes 43 b may serve to adsorb moisture. Theporous silica layer 43 may be transparent before and after moistureadsorption.

The adsorption holes have a diameter of approximately 0.5 to about 100nm, preferably approximately 10 to about 30 nm. Formation of theadsorption holes with a diameter of less than 0.5 nm may be difficult.On the other hand, adsorption holes with a diameter of greater than 100nm may provide insufficient adsorption.

An organic EL device of the present invention can be used for frontemission, rear emission, or bidirectional emission, depending on thematerial used for the porous oxide layer. In detail, when the porousoxide layer is kept transparent before and after moisture adsorption,e.g., when the porous oxide layer is composed of a transparent poroussilica, an organic EL device of the present invention can be used forfront emission. On the other hand, when the porous oxide layer is keptopaque before and after moisture adsorption, an organic EL device of thepresent invention can be used for rear emission.

There are no particular limitations on a driving method for an organicEL device of the present invention. Both passive matrix (PM) driving andactive matrix (AM) driving are possible.

The following are several examples. They are not intended to serve tolimit the scope of the invention but to assist the reader inunderstanding how to achieve the advantages and benefits of theinvention.

Example 1

Ammonia water (NH₄OH) was added to 30 g of H₂O to adjust the pH of aresultant solution to 10. 10 g of TEOS was then added thereto andstirred at an elevated temperature for 3 hours or more. Nitric acid wasadded to a resultant mixture to adjust the pH of the resultant mixtureto about 0.5 to 1.0.

1 g of a water-soluble acrylic resin solution (30 wt %) was added to themixture and stirred to obtain a uniform solution.

The uniform solution was coated on a soda glass substrate that wasrotating at 180 rpm for 120 seconds. Next it was dried in a drying ovenfor about 2 minutes to remove residual solvent. The resultant productwas calcined at 500° C. for 30 minutes to form a porous silica layer.

After cleaning the soda glass substrate with the porous silica layer, asealant was coated onto at least a side of the glass substrate with theporous silica layer and at least a side of a glass substrate with afirst electrode, an organic film, and a second electrode. Then both theglass substrates were joined to complete an organic EL device.

Example 2

In this example, 10 g of TEOS was added to a mixture of 30 g of H₂O and10 g of EtOH and was stirred for more than 30 minutes to carry outhydrolysis. Then 5 g of CaCl₂ was added to a resultant mixture anddissolved to prepare a composition for porous silica formation.

The composition was coated on a soda glass substrate that was rotated at180 rpm for 120 seconds. It was then dried in a drying oven for about 2minutes to remove residual solvent. The resultant was calcined at 500°C. to form a porous oxide layer.

The glass substrate with the porous oxide layer was cleaned. Then asealant was coated on at least a side of the glass substrate with theporous oxide layer and at least a side of a glass substrate with a firstelectrode, an organic film, and a second electrode. Then both the glasssubstrates were joined to complete an organic EL device.

Example 3

An organic EL device was completed in the same manner as in Example 2except that 5 g of LiBr instead of CaCl₂ was added to the compositionfor porous silica formation.

Example 4

NH₄OH was added to 30 g of H₂O to adjust the pH of a resultant solutionto 10. 10 g of TEOS was then added thereto and stirred with heating for3 hours or more. Nitric acid was added to a resultant mixture to adjustthe pH of the resultant mixture to about 0.5 to 1.0.

1 g of a water-soluble acrylic resin solution (30 wt %) was added to themixture and stirred to obtain a uniform solution.

The uniform solution was coated on a soda glass substrate that wasrotated at 180 rpm for 120 seconds. It was then dried in a drying ovenfor about 2 minutes to remove residual solvent. The resultant productwas calcined at 500° C. for 30 minutes to form a porous silica layer.

Then a mixture of 40 g of CaCl₂ and 60 g of water was coated on theporous silica layer and thermally treated to form a porous oxide layerin which CaCl₂ was infiltrated in the porous silica layer.

After cleaning the glass substrate with the porous oxide layer, asealant was coated onto at least a side of the glass substrate with theporous oxide layer and at least a side of a glass substrate with a firstelectrode, an organic film, and a second electrode. Then both the glasssubstrates were joined to complete an organic EL device.

Comparative Example 1

An organic EL device was completed in the same manner as in Example 1except that the porous silica layer was not formed on the soda glasssubstrate.

The porous silica layer according to Example 1 exhibited excellent filmcharacteristics such as a thickness of about 6.5 μm, a refractive indexof 1.25, and porosity of about 50%. Also, the porous silica layer wastransparent and had no defects such as cracks. These results can beeasily identified by the transmission electron microphotograph (TEM) ofthe microstructure of the porous silica layer of Example 1 shown in FIG.4.

The images of the organic EL devices according to Example 1 andComparative Example 1 were observed using a microscope at 70° C., 90% RHwith time, and the results are shown in FIGS. 3 and 5.

As shown in FIGS. 3 and 5, the organic EL device according to Example 1exhibited remarkably enhanced life span characteristics, relative to theorganic EL device according to Comparative Example 1.

The organic EL devices according to Examples 2-4 exhibited life spancharacteristics similar to those in Example 1.

An organic EL device of the present invention provides the followingadvantages.

First, an unetched flat glass can be used instead of an etched glass asa front substrate. Thus structural weakness (in terms of fractureproperties) caused by using the etched glass can be overcome.

Second, a front substrate has a porous oxide layer that adsorbs moistureand oxygen on a lower surface thereof. Thus there is no need to use aseparate desiccant material. Also, the organic EL device can be used forfront emission, rear emission, or both-direction emission, according toa material used for the porous oxide layer.

Third, just one coating can ensure easy formation of the porous oxidelayer uniformly coated on a wide area, as compared to a conventionalsol-gel method for thick film formation. Thus the porous oxide layer hasexcellent adsorption of moisture and oxygen.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

1. A method of manufacturing an organic electroluminescent device,comprising: preparing a first substrate having stacked, on a surfacethereof, an organic electroluminescent (EL) unit comprising a firstelectrode, an organic film, and a second electrode; coating acomposition comprising a silicon alkoxide and a polar solvent onto asurface of a second substrate that will be an interior surface followedby thermal treatment to form a porous silica layer; coating a sealantonto at least a side of each of the first substrate and the secondsubstrate corresponding to outside the organic EL unit; and joining thefirst substrate and the second substrate.
 2. The method of claim 1,wherein the composition of the coating step further comprises one ormore selected from the group consisting of alkaline metal salt, alkalineearth metal salt, metal halide, metal sulfate, and metal perchlorate. 3.The method of claim 2, wherein the alkaline metal salt comprises one ormore selected from the group consisting of potassium acetate, potassiumnitrate, sodium acetate, and sodium nitrate; wherein the alkaline earthmetal salt comprises one or more selected from the group consisting ofcalcium acetate, calcium nitrate, barium acetate, and barium nitrate;wherein the metal sulfate comprises one or more selected from the groupconsisting of Li₂SO₄, Nai₂SO₄, CaSO₄, MgSO₄, CoSO₄, Ga₂(SO₄)₃, Ti(SO₄)₂,NiSO₄; the metal halide comprises one or more selected from the groupconsisting of CaCl₂, MgCl₂, SrCl₂, YCl₂, CuCl₂, CsF, TaF₅, NbF₅, LiBr,CaBr₃, CeBr₄, SeBr₂, VBr₂, MgBr₂, BaI₂, or MgI₂, and the metalperchlorate is Ba(ClO₄)₂, and Mg(ClO₄)₂.
 4. The method of claim 1,wherein the composition of the coating step further comprises an acrylicresin.
 5. The method of claim 1, further comprising after the step ofcoating a composition, coating on the porous silica layer a solvent anda second composition comprising one or more selected from the groupconsisting of alkaline metal salt, alkaline earth metal salt, metalhalide, metal sulfate, and metal perchlorate.
 6. The method of claim 1,further comprising after the step of coating the composition, coating athird composition comprising a metal halide and a solvent on the poroussilica layer.
 7. The method of claim 6, wherein the metal halidecomprises one or more material selected from the group consisting ofCaCl₂, MgCl₂, SrCl₂, YCl₂, CuCl₂, CsF, TaF₅, NbF₅, LiBr, CaBr₃, CeBr₄,SeBr₂, VBr₂, MgBr₂, BaI₂, and MgI₂.
 8. The method of claim 1, whereinthe silicon alkoxide comprises one or more selected from the groupconsisting of tetraethylorthosilicate and tetramethylorthosilicate. 9.The method of claim 1, wherein the composition of the coating stepfurther comprises about 0.1 to about 0.9 moles of a catalyst forfacilitating a hydrolysis reaction, for each mole of the siliconalkoxide.
 10. The method of claim 1, wherein the thermal treatment isperformed at a temperature of about 100 to about 550° C.